Whooping cough, or pertussis, is a non-invasive respiratory infection established by the adherence of the bacteria Bordetella pertussis (Bp) to the cilia of human respiratory cells. The disease is virtually 100% contagious and sometimes fatal. It is world wide, serious and often epidemic. An epidemic in Japan in 1979 resulted in 41 deaths from a total of 13,105 cases.
The incidence of pertussis in a highly vaccinated population as in the United States is estimated at about 300 per 100,000. In less developed countries where vaccination is not the norm infant mortality due to pertussis is close to this same figure. The World Health Organization currently recommends that every child, worldwide, receive protection from whooping cough.
The current whole cell vacine available in the United States and Europe is 70% to 90% effective, but has an unacceptably high rate of toxicity including death, particularly amongst infants who are the prime targets of the disease. Moreover, both children and adults who have been protected by vaccination may be infected without clinical manifestations. This population colonized with the bacteria is a source of infections to others.
An additional problem with control of pertussis is that it is difficult to identify until after the disease has become established in the patient. Thus the physician's role is often reduced to attempts to attenuate the clinical manifestations of pertussis, to prevent secondary infections, and to treat superinfections with other pathogenic organism, for example Haemophilus influenzae, group A streptococci and pneumonococci. Such superinfections are not uncommon, have grave prognoses and often result in death.
A system which could be useful in the control and possible eradication of pertussis, which would protect infants without exposure to potentially toxic vaccines and at the same time protect adults and eliminate both children and adults as sources of infection would be:
1. Defer use of vaccines by conferring passive protection on infants until they are at least six months of age to permit the infant's immune system to mature and avoid the possibility of serious adverse reactions associated with early vaccination.
2. Use of vaccines which would be safe and effective with older infants and adults.
3. Use of vaccines with pregnant women and possible transfer of immunity to infants in utero and through the colostrum.
The problem with this proposed regimen is that heretofore there has been no practical method for conferring passive protection on infants pending vaccination. An agent capable of generating passive protection would also be useful to protect individuals at risk because of exposure to Bp. This could include newborns, children in school, hospital personnel, unvaccinated children and adults, and immunocompromised children. The value of such a prophylactic agent would be enhanced if it could also be used to treat an existing infection.
As indicated above, Bp infects humans by adherence to the cilia of the epithelial cells of the respiratory tract. The infection establishes itself when the organism multiplies and spreads along the same cilia or to adjacent cilia. An agent to prevent the original infection and/or expansion from the original infection site would be of great therapeutic value. Such agents have now been found.